In a variety of sports, such as golf, tennis, baseball and the like, a person's grip on the handle of the club (or other sporting implement) can be critical to the degree of success the person has in the sport. For example, in golfing, many golfers are unable to consistently produce a smooth swing without jerking or otherwise changing strength of their grip midswing. Such jerking or changes in grip (or strength of grip) disrupt the smooth flow of a swing, causing the golfer to slice, hook, or otherwise inaccurately hit the ball. Conversely, players who are able to avoid such dysfunctions in their swing are able to more consistently hit the ball accurately.
Similar smoothness of stroke is desirable in many other sports utilizing hand-held implements, such as tennis rackets, baseball bats, and the like, and even firearms (where the sportsman frequently may jerk when pulling the trigger or prematurely move the firearm in anticipation of the firearm's natural recoil when discharged). Thus, in many such areas of sporting, them is a need for a biofeedback device which will signal to the sportsman significant changes in the sportsman's grip (or strength of grip) on the handle of the sporting implement being utilized.
Devices attempting to fill this need have been proposed. For example, U.S. Pat. No. 3,323,367 (R. W. Searle) describes a "grip indicator" having a pair of resistive sensors connected in a conventional bridge circuit to a zero-centered ammeter mounted on the shaft of a golf putter. One of the pressure sensitive resistive sensors is located on the handle in a position corresponding to the left hand position of the golfer, and the other sensor is positioned for the right hand. By viewing the position of the needle on the ammeter, the golfer can visually confirm that his grip is equally balanced between his two hands. Although the invention is also described as being applicable to tennis racket handles, the utility of the device is somewhat limited by the need for the sportsman to actually view the position of the needle on the ammeter during use of the putter or racket. This limitation significantly affects the utility of the device when used other than in gentle strokes (such as with a putter).
U.S. Pat. No. 4,138,118 (D. R. Budney) provides an improvement over the Searle indicator, in that Budney connects two or three analog pressure-sensitive transducers to a chart recorder which graphically depicts the amount of force being exerted on each pressure transducer during the swing of a golf club. The devices uses two, or, at most, three transducers on the handle of the club, independently charting the force applied to each such transducer. Analysis of the printout of the chart recorder reveals the faults in the player's swing, permitting after-the-fact diagnosis of the swing. The device does not provide real time feedback to the golfer, however, and requires an electrical cable connecting the club to a portable chart recorder, making the device somewhat cumbersome to utilize.
U.S. Pat. No. 4,861,034 (S. Y. Lee) describes a grip training device attachable to (and removable from) the handle of a golf club. An elongated pressure sensitive switch is mounted on the underside of the handle, and is responsive to the grip pressure of the golfer. The switch is formed of three resilient conducting strips spaced from one another by compressible foam blocks. When grip pressure is sufficient to compress one of the resilient, conducting strips against an adjacent strip, a circuit is completed causing a battery powered buzzer to emit an audible signal. The Lee device is relatively thick in relation to the thickness of a golf club handle, and consequently affects the normal grip of the golfer. Moreover, the device provides pressure sensing only on the underside of the club handle, and therefore cannot detect pressure of the golfer's hands against other portions of the handle.
In addition to the above referenced patents, other similar biofeedback devices have been proposed. In most cases, however, such devices are complicated to use, interfere with ordinary grip and/or use of the sporting implement, and/or are quite expensive.